Corrosion inhibitor comprising azole and cellulose nanocrystals

ABSTRACT

The present invention relates to a corrosion inhibitor. The corrosion includes an azole and a plurality of cellulose nanocrystals. The cellulose nanocrystals are combined with monovalent cationic counterions according to one aspect. The monovalent cationic counterions are sodium ions according to one example. The cellulose nanocrystals may be in dried solid form. According to a further aspect, there is provided a process for the use of cellulose nanocrystals in inhibiting corrosion. The process includes the step of providing an azole. The process further includes the step of adding cellulose nanocrystals to the azole. According to another aspect, there is provided a process for inhibiting corrosion of metal equipment where water can reside. The process includes adding an effective corrosion inhibiting amount of a corrosion inhibitor composition. The corrosion inhibitor composition includes an azole and cellulose nanocrystals.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional application No. 61/668,001 filed in the United States Patent and Trademark Office on Jul. 4, 2012, the disclosure of which is incorporated herein by reference and priority to which is claimed.

FIELD OF THE INVENTION

The present invention relates to a corrosion inhibitor. In particular, the invention relates to a corrosion inhibitor comprising azole and cellulose nanocrystals.

DESCRIPTION OF THE RELATED ART

It is known per se to use azole compounds to inhibit corrosion. For example, U.S. Pat. No. 4,134,959 to Menke et al. provides a composition and method for inhibiting corrosion. The composition consists essentially of an azole and a water-soluble phosphate in an effective combination to inhibit corrosion in both ferrous and non-ferrous metals.

However, azole compounds are relatively expensive. There is accordingly a need for an effective corrosion inhibitor that is less costly.

BRIEF SUMMARY OF INVENTION

It is an object of the present invention to provide, and the present invention discloses herein, an improved corrosion inhibitor that overcomes the above disadvantages.

According to one aspect, there is provided a corrosion inhibitor. The corrosion includes an azole and a plurality of cellulose nanocrystals.

The cellulose nanocrystals are combined with monovalent cationic counterions in one embodiment. The monovalent cationic counterions are sodium ions according to one example. The cellulose nanocrystals may be in dried solid form.

According to a further aspect, there is provided a process for the use of cellulose nanocrystals in inhibiting corrosion. The process includes the step of providing an azole. The process further includes the step of adding cellulose nanocrystals to the azole.

According to another aspect, there is provided a process for inhibiting corrosion of metal equipment where water can reside. The process includes adding an effective corrosion inhibiting amount of a corrosion inhibitor composition. The corrosion inhibitor composition includes an azole and cellulose nanocrystals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Cellulose nanocrystals are typically in the form of rod shaped fibrils or needles. The fibrils may, for example, have a length/diameter ratio of about 20 to 200, a diameter preferably less than about 60 nm, a diameter more preferably in the range of 4 nm to about 15 nm, and a length of about 150 nm to about 350 nm. Cellulose nanocrystals as referred to herein may alternatively be referred to as nanocrystalline cellulose (trademark), cellulose nanofibres or cellulose whiskers. Dried forms of cellulose nanocrystals may obtained via acid hydrolysis, as for example set out in International Patent Publication No. WO 2010/066036 A1 to Beck et al, the disclosure of which is incorporated herein by reference. Cellulose nanocrystals may be purchased at CelluForce Inc., which has an office at 625 President Kennedy, Montreal, Québec, H3A 1K2.

A series of corrosion tests were performed the results of which are shown in Table 1 set out below.

TABLE 1 Coupon Weight Loss in mills per year (mpy) Salt Solution with Salt Solution with Azole and Cellulose Cellulose Nanocrystals Nanocrystals Salt Solution (dried-form, Na-CNC) Salt Solution (dried-form, Na-CNC) (control) added to the solution with Azole added to the solution Aluminium A1 = 0 mpy   A2 = 0.4 mpy A3 = 0.1 mpy A4 = 0 mpy Coupons (A) Brass B1 = 0.1 mpy B2 = 0.2 mpy B3 = 0 mpy   B4 = 0 mpy Coupons (B) Steel S1 = 1.2 mpy S2 = 1.7 mpy S3 = 0.9 mpy   S4 = 0.6 mpy Coupons (S)

Corrosion rates were measured by immersing coupons of aluminum A-2024-T3 (A), yellow brass UNS C27000 (B) and carbon steel 4130 (S) in typical seawater compositions and measuring the loss of mass due to corrosion after 33 days. The coupons were left at ambient temperature and remained sealed within jars.

The mass of each coupon was determined before and after the 33 day period to an accuracy of ±10⁻⁵ grams. Mils per year (mpy) rates were obtained thereby following the protocol outlined in the NACE International Corrosion Engineers Reference Book, 2^(nd) Edition, at set out on pages 78 and 79 therein. This book may be obtained at NACE International, which has an address at 1440 South Creek Drive, Houston, Tex., 7084-4906, USA.

Coupons A1, B1 and S1 were tested in jars containing control test salt solutions were used comprising 500 grams of water and 25 grams of sea salt, as seen in table 2. The sea salt used in this example was Agenco(trademark) sea salt, which may be purchased at Whole Foods Market IP. L.P., having an address at 2285 W 4th Ave, Vancouver, British Columbia, Canada. This resulted in corrosion rates for the aluminum (A1), brass (B1) and steel (S1) coupons of 0 mills per year (mpy), 0.1 mpy and 1.2 mpy, respectively.

TABLE 2 Mass of Chemicals in Formulation (grams) Cellulose Water Sea Salt Nanocrystals Azole (grams) (grams) (grams) (grams) Salt Solution 500 25 0 0 (Coupons A1, B1, and S1) Salt Solution with 500 25 34 0 Cellulose Nanocrystals (dried-form, Na-CNC) added to the solution (Coupons A2, B2 and S2) Salt Solution with Azole 500 25 0 34 (Coupons A3, B3 and S3) Salt Solution with Azole 500 25 34 34 and Cellulose Nanocrystals (dried-form, Na-CNC) added to the solution (Coupons A4, B4 and S4)

Coupons A2, B2 and S2 were also tested in jars having 500 grams of water, 25 grams of sea salt and 34 grams of cellulose nanocrystals, as seen in Table 2. The cellulose nanocrystals used throughout the testing were in dried solid form in this example, where its proton counterion is replaced with a monovalent cationic counterion. In this example, the monovalent cationic counterions are sodium ions. The cellulose nanocrystals were thus sodium-form in this example. However, other forms of monovalent cationic counterions may be used, such as K⁺, Li⁺, NH₄ ⁺ and tetraalkylammonium (R₄N⁺), protonated trialkylammonium (HR₃N⁺), protonated dialkylammonium (H₂RaN⁺), and protonated monoalkylammonium (H₃RN⁺) ions for example.

This resulted in corrosion rates for the aluminum (A2), brass (B2) and steel (S2) coupons of 0.4 mpy, 0.2 mpy and 1.7 mpy, respectively. In other words, the cellulose nanocrystals increased corrosion rates for each of the coupons tested.

Coupons A3, B3, and S3 were further tested in jars having 500 grams of water, 25 grams of sea salt and 34 grams of azole, as seen in Table 2. The azole used in this example was benzotriazole (BTA), a well-known inhibitor, though this is not strictly required and other azoles can be used. For example, the azole can be selected from one or more of the group consisting of: tolyltriazole, benzotriazole, 1,2benzisothiazoline-3-1, 2-benzimidazolone, 4,5,6,7-tetrahydrobenzotrazole, tolylimidazolone, 2(5-ethyl-2-pyridyl)benzimidazole, and 2-mercaptobenzothiazole. According to one preferred aspect, the azole can be selected from the group consisting of tolyltriazole, benzotriazole, and 2-mercaptobenzothiazole. The water, salt and azole composition resulted in corrosion rates for the aluminum (A3), brass (B3) and steel (S3) coupons of 0.1 mpy, 0.9 mpy and 0 mpy, respectively. In all but the case for the aluminium coupon A3, the solutions containing azole thus inhibited the corrosion rates for of the coupons tested compared to the coupons A1, B1 and S1 subjected to the control salt solution.

Coupons A4, B4, and S4 were tested in jars having 500 grams of water, 25 grams of sea salt, 34 grams of cellulose nanocrystals and 34 grams of azole, as seen in Table 2.

Unexpectedly, this resulted in corrosion rates for the aluminum (A4), brass (B4) and steel (S4) coupons of 0 mpy, 0.6 mpy and 0 mpy, respectively. It can thus be seen in that compared to azole alone, a combination of azole and cellulose nanocrystals provides a synergistic improvement in corrosion inhibition. The corrosion rate of the aluminium coupon was lowered, the corrosion rate of the brass remained at zero, and the corrosion rate of the steel went down by 30 percent. It has thus been discovered that combining azole compounds with cellulose nanocrystals provides a synergistic effect in inhibiting corrosion for ferrous and non-ferrous metals. This may therefore reduce the amount of azole and/or cellulose nanocrystals required to effectively inhibit corrosion.

It will be understood by someone skilled in the art that many of the details provided above are by way of example only and are not intended to limit the scope of the invention which is to be determined with reference to at least the following claims. 

1. A corrosion inhibitor comprising: an azole; and a plurality of cellulose nanocrystals.
 2. The corrosion inhibitor as claimed in claim 1 wherein the cellulose nanocrystals are in dried solid form.
 3. The corrosion inhibitor as claimed in claim 1 wherein the cellulose nanocrystals are combined with monovalent cationic counterions.
 4. The corrosion inhibitor as claimed in claim 1, wherein the cellulose nanocrystals are in sodium-form.
 5. The corrosion inhibitor as claimed in claim 3 wherein the monovalent cationic counterions are sodium ions.
 6. The corrosion inhibitor as claimed in claim 1 for use in inhibiting corrosion in ferrous metals.
 7. The corrosion inhibitor as claimed in claim 1 for use in inhibiting corrosion in non-ferrous metals.
 8. The corrosion inhibitor as claimed in claim 1, wherein the azole is one or more from the group consisting of: tolyltriazole, benzotriazole, and 2-mercaptobenzothiazole.
 9. The corrosion inhibitor as claimed in claim 1, wherein the azole is one or more from the group consisting of: tolyltriazole, benzotriazole, 1,2benzisothiazoline-3-1, 2-benzimidazolone, 4,5,6,7-tetrahydrobenzotrazole, tolylimidazolone, 2(5-ethyl-2-pyridyl)benzimidazole, 2-mercaptobenzothiazole.
 10. The corrosion inhibitor as claimed in claim 1 wherein the azole is tolyltriazole.
 11. A metal-cutting fluid using the corrosion inhibitor as claimed in claim
 1. 12. A process for the use of cellulose nanocrystals in inhibiting corrosion, comprising the steps of: a) providing an azole; and b) adding cellulose nanocrystals to the azole.
 13. The process as claimed in claim 12, further including adding water to the azole and the cellulose nanocrystals.
 14. The process as claimed in claim 12, further including adding the azole and the cellulose nanocrystals to water having salt dissolved therein.
 15. The process as claimed in claim 13, further including dispersing the azole and cellulose nanocrystals within the water.
 16. The process as claimed in claim 12 for inhibiting corrosion of metal equipment where water can reside, the process including adding an effective corrosion inhibiting amount of the azole and the cellulose nanocrystals.
 17. A corrosion inhibitor consisting essentially of: an azole; and a plurality of cellulose nanocrystals.
 18. The corrosion inhibitor as claimed in claim 17, wherein the azole is one or more from the group consisting of: tolyltriazole, benzotriazole, and 2-mercaptobenzothiazole.
 19. The corrosion inhibitor as claimed in claim 17, wherein the azole is one or more from the group consisting of: tolyltriazole, benzotriazole, 1,2benzisothiazoline-3-1, 2-benzimidazolone, 4,5,6,7-tetrahydrobenzotrazole, tolylimidazolone, 2(5-ethyl-2-pyridyl)benzimidazole, and 2-mercaptobenzothiazole.
 20. The corrosion inhibitor as claimed in claim 17 wherein the azole is tolyltriazole. 